Generally, thickness detection of banknote is a necessary function in the money detecting apparatus and the ATM apparatus, and the tapes, folded corners on the banknote can be used to identify the thickness of the banknote therefore recognize the unqualified banknote.
The most commonly used repair method of a sheet, such as paper, bank notes, etc., is to reattach a layer of material for reinforcement. For example, the broken banknotes are usually using transparent tape to paste to avoid the continuously damage. As the banknotes will go through the recovery process, so the banking equipment would spend lots of time and money developing device for identifying the accuracy of the tape on the banknotes.
The device for measuring the thickness variations caused by adhesive tapes must have a high degree of resolution to determine the thickness variations since the typical thickness of adhesive tapes is very small.
There are many methods for measuring the thickness variations caused by adhesive tapes, which can be divided into two types: non-contact type method and contact type method. In the non-contact portion, ultrasound (U.S. Pat. Nos. 4,446,735 and 7,748,274) or capacitive sensing (U.S. Pat. No. 8,028,990) are the most common methods. However, both methods are susceptible to non-banknote factors, such as mechanical high-frequency or humidity. Thus, people prefer to use the contact type method for measuring the thickness variations caused by adhesive tapes.
The contact type method can be divided into friction type and roller type. The friction type method, such as U.S. Pat. No. 8,651,481, and then using the piezoelectric element to output the signal. The roller type method can be presently the main design direction, such as U.S. Pat. Nos. 4,550,252, 4,693,010, 6,913,260, 7,743,523, 8,091,889, 8,496,246, 8,582,123, and 8,610,441. In these patents, rollers are used to contact the objects to measure the thickness variations and represent the value on the wheel displacement; the roller would generate a rotational displacement due to the limitation of external rotation axis. The different patents use different sensing elements to output the signals of thickness variations.
In the constraint condition of the rotation axis of a link mechanism, the roller type thickness variation detector would generate a rotational displacement (angular movement) in existing devices. Without adding any mechanical components, such as connecting rods, the side face, signal measuring items (such as metal plate) and the detecting components would generate a relative rotational displacement (angular displacement) and cannot generate a completely parallel or vertical displacement t. If coils type sensor is used, the detection accuracy of the displacement detector is decreased.
For example, the device for detecting thickness and thickness variation of existing device 100′ (please refer to FIG. 1 and FIG. 2, which is a schematic diagram of U.S. Pat. No. 8,496,246). which is used for detecting thickness and thickness variation of a sheetlike object 200, includes: first guiding component 1′, second guiding component 2′, and the sheetlike objection 200 is delivered between the first guiding component 1′ and second guiding component 2′, wherein the second guiding components 2′ are opposite to first guiding component 1′, and the second guiding components 2′ are arranged in line, a deviation which is the second guiding component 2′ related to the first guiding component 1′ while the sheetlike object 200 passed through the first guiding component 1′ and those second guiding components 2′, due to the thickness variation of the sheetlike object 200′; a flat spring 3′, having a sensing face 35′ which connects with second elastic displacement 2′ through movable fixing component 34′, and the flat spring 3′, the sensing face 35′, movable fixing component 34′ and the second guiding component 2′ are connected and fixed with a stable fixing component 5′ through a rotation axis 51′; when the second guiding component 2′ has a deviation in relation to the first guiding component 1′, the displacement of sensing face 35′ occurs immediately, position sensor 4′ on which sensor coil 41′ is used to detect the displacement of sensing face 35′. However, the flat spring 3′ generates an angle of deviation grounded on rotation axis 51′ in relation to the position sensor 4′, and the sensing face 35′ cannot generate parallel or vertical displacement; particularly the tilt of the sensing face 35′ causes a decrease in accuracy of the sensor coil 41′ for detection.
In view of the above-mentioned problem, how to develop a device for improving the accuracy of displacement measurement without any angular displacement or inclined displacement is an urgent problem in relevant field.